1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head that discharges a liquid, and more specifically, to a method for manufacturing an inkjet recording head.
2. Description of the Related Art
As a method that employs a liquid discharge head that discharges a liquid, an inkjet recording method is known.
An inkjet recording head adapted for use in the inkjet recording method typically has a fine recording liquid discharge opening, a liquid channel for allowing liquid to flow, and a liquid discharge energy generating element provided on a part of the liquid channel. Examples of previously known methods for manufacturing such an inkjet recording head are described below.
According to a manufacturing method disclosed in U.S. Pat. No. 5,331,344, an inkjet recording head is manufactured by forming a first photosensitive material layer in which an ink channel is to be formed, then performing a first pattern exposure for ink channel formation on the first photosensitive material layer by using a mask, then forming a second photosensitive material layer with a photosensitive spectrum region different from that of the first photosensitive material layer on the first photosensitive material layer, and then performing a second pattern exposure for discharge opening formation on the second photosensitive material layer with light having a different wavelength from light used in the first pattern exposure for ink channel formation.
According to another method disclosed in U.S. Pat. Nos. 6,447,102 and 6,520,627, an inkjet recording head is manufactured by laminating two materials with different sensitivities, the difference in sensitivity being realized by the action of a dye, and being irradiated with light with varied intensities.
More specifically, a negative resist lower layer having a slow cross-linking rate and a low sensitivity with the addition of a dye is formed on a substrate, and a negative resist upper layer having a high sensitivity without the addition of a dye is formed on the negative resist lower layer. Then, the negative resist upper and lower layers are subjected to a first pattern exposure for forming an ink channel wall, and the negative resist upper layer is subjected to a second pattern exposure for forming a discharge opening. Lastly, development is performed and an uncrosslinked portion is removed, thus forming the ink channel and discharge opening patterns.
In the former manufacturing method, however, since spin coating is used to form the second photosensitive material layer on the first photosensitive material layer, an unexposed portion of the first photosensitive material layer can be dissolved in a solvent in which the second photosensitive material dissolves.
Additionally, according to the latter manufacturing method, which is disclosed in U.S. Pat. Nos. 6,447,102 and 6,520,627, the difference in sensitivity to light between the upper and lower resists can be insufficient.
In either method, when development is performed by using a developer, the border between a soluble area and an insoluble area with respect to the developer can be unclear. Therefore, the development is susceptible to variations in concentration of the developer, and as a result, the thickness of an orifice plate in which a discharge opening is formed can vary widely. This prevents an inkjet recording head with a very fine ink channel from being manufactured with high yield.